The on-site hydrogen supply is a key issue for the commercialization of the fuel cells, which is one of the important ways for realizing a hydrogen-economy society. Composite NaNH2–NaBH4 is regarded as a promising high-capacity hydrogen storage material. In this paper, the composite NaNH2–NaBH4 (2/1) was synthesized via a solid-state ball milling method. To improve the hydrogen generation kinetics, a multiplex metal boride Mg–Co–B was selected as the catalyst. It was found that Na3BN2 and metal Na were byproducts in the thermal decomposed sample by X-ray diffraction analysis. Thermogravimetry and differential thermal analysis indicated that the main decomposition stages of the catalyst promoted NaNH2–NaBH4 material were split into three stages. The activation energy of the Mg–Co–B promoted NaNH2–NaBH4 (2/1) material below 300 °C was 76.4 KJ/mol, which is only 47.9% of that of the pristine NaNH2–NaBH4 (2/1), and implying much better hydrogen generation kinetics.

In the present work, specimens of the metastable austenitic stainless steel AISI 347 with different surface morphologies were investigated in stress-controlled fatigue tests in the high cycle fatigue (HCF) regime at ambient temperature. Specific surface morphologies were generated by cryogenic turning with CO2 snow cooling. As a result of the metastable austenite microstructure, phase changes from paramagnetic austenite to ferromagnetic martensite take place in the near-surface regime during cryogenic turning as well as in the whole specimen volume during monotonic and/or cyclic elastic–plastic deformation. The metastability of AISI 347 was characterized according to the M S-temperature determined from the chemical composition and by X-ray diffraction measurements with in situ cooling. Microhardness and strength of both phases were measured. Near-surface microstructure was analyzed by optical and scanning electron microscopy after focused ion beam preparation. Besides a partially martensitic surface layer, a thin nanocrystalline layer, both induced by cryogenic turning, was observed. In case of cyclic loading, the martensitic surface layer leads to a reduction of plastic strain amplitude as well as a retardation of crack initiation and consequently to an increase in fatigue life.

Palladium (Pd) nanostructures have been actively adapted for various applications and their properties and applicability closely depend on their shape, size, and density. In this paper, the evolution of self-assembled Pd nanostructures on the hexagonal c-plane GaN is presented by the systematical control of Pd deposition amount (DA) at distinctive temperatures. Pd nanostructures of various configurations, sizes, and densities are demonstrated based on the solid-state dewetting of Pd thin films and a clear distinction in the growth regimes is observed. Three growth regimes are clearly observed depending on the variation of DA, i.e., (i) the agglomeration of Pd nanoparticles, (ii) the coalescence of wiggly Pd nanostructures, and finally (iii) the growth of nanovoids and layers. Owing to the temperature-dependent dewetting process, the growth regimes are markedly shifted, resulting in the distinctive Pd nanostructures within the identical DA range. The results are discussed in conjunction with the surface diffusion, Volmer–Weber and coalescence growth model, and surface/interface energy minimization mechanism. In addition, the evolution of optical properties, emission band, and lattice properties are probed by reflectance, photoluminescence, and Raman spectroscopy, which exhibit varying spectral intensity and peak positions according to the surface morphology of Pd nanostructures.

In a hot forming process, the study of the interface tool/product proves important. This study focuses on the influence of the third body in the case of pin-on-disc in an open contact. The objective of this work was to identify the third body-particle circulation mechanisms at high temperatures. The “wear and friction” tests were conducted with an open sliding contact on pairs of X40CrMoV5/Fe360B steels under a normal force of 70 N at 600 °C and with a speed of rotation of the disc of 50 rev/min. The pin material was X40CrMoV5 (AISI H13) steel and the disc material was Fe360B steel. Scanning electronic microscope, energy-dispersive spectroscopy (EDS), and X-ray diffractometer explored the development surface damage and oxides tribo-oxides. It was concluded that various types of the third body particles were present in the contact. The wear mechanism on the X40CrMoV5 pin in a high temperature contact is proposed.

Crystallized FeB and Fe2B powders were synthesized by a molten salt method with elemental Fe and B powders as starting materials. The results indicated that the presence of molten NaCl/KCl salts and the excess of Fe or B powders were essential to obtain pure FeB or Fe2B powders. The formation mechanism of iron borides was investigated by examining the phase compositions of the obtained products with different molar ratio of Fe/B. It was found that Fe powders firstly reacted with B powders to form Fe2B phase, and FeB phase formed from the reaction between Fe2B and excessive B. The as-synthesized FeB and Fe2B powders had a uniform short-rod and plate like morphology, respectively. Both FeB and Fe2B exhibited typical soft magnetic behavior. The saturation magnetization and the coercivity were 36.4 emu/g and 15.5 kA/m for FeB, 126.9 emu/g and 6.1 kA/m for Fe2B, respectively. The electrochemical performances of the as-synthesized FeB powders were evaluated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance test.

The erosion behavior of a directionally solidified Fe–B alloy containing 3.5 wt% B in the different velocities of flowing liquid zinc is investigated by X-ray diffraction and scanning electron microscopy to clarify the effect of interaction between Fe2B and the erosion products on erosion performance using a rotating-disk technique. The results indicate that the Fe–B alloy erodes at a low and steady rate in flowing liquid zinc. The microstructure of erosion layers of the directionally solidified Fe–B alloy depends on the orientation relation between the growth direction of Fe2B phase and the erosion surface. When the growth direction of Fe2B is perpendicular to the erosion surface, the Fe2B and the erosion compounds form a compact and stable combining layer that effectively inhibits the erosion of flowing liquid zinc and further improves the erosion resistance of Fe–B alloy.

It is important to fabricate iron-based nitride/conductive material composite to obtain good catalytic performance. In this work, Fe2N nanoparticles with diameter of approximately 30 nm have been successfully dispersed on the surface of nitrogen-doped graphite oxide (NrGO) by a facile sol–gel method and further ammonia atmosphere treatment. XPS, XRD, Raman, and TEM proved that Fe2N nanoparticles are well monodispersed, and nitrogen atoms are doped in NrGO. The composite possessed two merits, that is, the more catalytic active site in Fe2N nanoparticles due to the well monodispersion, and fast electron transfer due to the nitrogen dope in rGO. With the proper ratio, the composite exhibited brilliant catalytic activity and durability in acidic media. It possesses overpotential of 94 mV to approach 10 mA/cm2, a small Tefel slope of 49 mV/dec, and maintains the good electrocatalytic activity for 10 h. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that the electrocatalyst possessed high catalytic active area and fast electron transfer. Our work may provide a new avenue for the preparation of low-cost iron-based nitride/NrGO composite for highly efficient electrochemical hydrogen evolution.

Extremely hard, wear-resistant SiC-bonded diamond materials with diamond contents of approximately 45–60% by volume can be prepared by pressureless infiltration of shaped diamond compacts with silicon. Materials with diamond grain sizes in the range of 10–100 µm can be produced having a free silicon content of less than 5 vol%. Components with large dimensions can be prepared as graded or ungraded materials. Graded components are composed of silicon infiltrated SiC base material with diamond–SiC composite layers of 0.1 mm by dip coating technology to several mm in thickness by doubled die pressing in regions with high loading. This creates the possibility of producing low-cost, wear-resistant components of various geometries and dimensions with bending strengths of 400–500 MPa, hardness values of 48 GPa, and fracture toughness levels of 4.5–5 MPa m1/2 for use in extreme wear conditions. Thermal conductivities of up to 500 W/(m K) were obtained, render these materials interesting for heat sinks.

A highly sensitive impedance sensor operating at room temperature has been developed for the quantitative determination of formaldehyde vapor. Nanostructured zinc oxide (ZnO) was synthesized by chemical reduction and used, in the form of a pellet, as the sensing material. Its performance was compared to that of the pellet made from commercial ZnO. Both samples were characterized by X-ray diffraction, Fourier transform infra-red spectroscopy, ultraviolet–visible spectroscopy, and atomic force microscopy techniques. Changes in impedance caused by formaldehyde in the concentration range from 100 to 800 ppm were measured and Nyquist plots revealed a systematic variation in impedance. The sensor response and formaldehyde concentration are exponentially correlated for both the laboratory synthesized and commercial ZnO samples. However, the lab-synthesized sample displays a better performance in terms of sensitivity, response, recovery, and stability. In addition, the response of the lab-synthesized sample is less sensitive to interferences by reducing gases such as ammonia, ethanol, methanol, and propanol.

The dissimilar metal inert-gas arc welding of aluminum alloy and ultrahigh strength steel was studied. The weld appearance was improved when welding wire was directed toward steel groove middle. The Al–steel joints have welding–brazing characteristics and include weld zone (WZ), bond zone (BZ), and interface zone (IZ). The welds with Al–Mg and Al–Cu welding wires consist of α-Al and β-Al3Mg2, and α-Al and Al2Cu, respectively. The IZ contains needle-like Fe4Al13 and lath-shaped Fe2Al5 layers. With increasing welding current, the interface layer thickness and joint cracking sensibility increased due to enhanced heat input and tensile stress in the joints. They were decreased effectively when using Al–Cu welding wire, as the constituent Cu could restrain the growth of interface layer and lower its hardness and brittleness. In particular, Al–Cu welding wire elevated the tensile strength of the Al-steel joints from 65 MPa for Al–Mg wire to 128 MPa.

The constitutive equation was established based on the consideration of strain compensation to describe the hot deformation behavior of low carbon reduced activation ferritic/martensitic (RAFM) steels at the temperatures of 850–1050 °C and the strain rates of 0.01–10 s−1. The result indicates that the flow stress is increased with the increase of strain rate but decreased with increase of deformation temperature. During the hot deformation process, the increase of temperature is beneficial to attain the complete dynamic recrystallization (DRX). However, excessively high temperature leads to grow up of dynamic recrystallized grain. Higher strain rate leads to finer recrystallized grains. The material constants (α, n, A) and deformation activation energy (Q) are calculated by the regression analysis. The increase of strain caused the decrease of Q, indicating the DRX occurred more easily. In addition, the developed constitutive equation could accurately predict the hot deformation behavior of the low carbon RAFM steel.

In this work, o-phenylenediamine-m-phenylenediamine copolymer dots (omCPs) with designed surface groups are synthesized and characterized. Here, we explored a simple, rapid semiquantitative detection system for Cu2+ with a wide detection range (5–7 orders of magnitude) based on the fluorescence in the solid state of omCPs and their tunable detection limits. The construction and application of the rapid semiquantitative detection system for Cu2+ are developed and demonstrated for the practical applications. What’s more, the detection limit can be modulated easily by adjusting the surface groups of these dots through the monomer dose control before the co-polymerization. Moreover, we demonstrated that this new technological approach is suitable for the semiquantitative determination of other ions pollutants (i.e., Na+, K+, Cu2+, Pb2+, Hg2+, and NO2 −) in environmental water.

The purpose of this work is, based on CAFE method, to study the microstructure evolution and optimize the quality of the large-scale titanium slab ingot during EBCHM. The nucleation parameters of the microstructure simulation of titanium ingot are determined based on one of the actual experimental results. For the determined parameters, our theoretical results are agreement with other experimental results. The effects of pouring temperature and pulling speed on the microstructure are presented based on CAFE method. The quantitative analyses of the simulated results show that with the pulling speed increasing, the number of grains decreases, whereas the mean grain radius increases under identical thermal condition; with the pouring temperature increasing, the mean grain radius increases under the given pulling speed. Our results are very important to obtain the optimal structure of the ingots by controlling pulling speed and pouring temperature.

A pure and (Fe–Ni) doped tin oxide thin films were formed on glass substrates by sol–gel dip coating method. Some characterization techniques are used as X-ray diffraction (XRD), UV–vis spectroscopy and atomic force microscopy (AFM) to study the effect of method conditions and dopants on the structural, morphological, and optical properties of thin films. According to XRD results, no phase attributed to Fe or Ni were detected, which suggests the incorporation of Fe and Ni in SnO2 network. All the diffraction peaks can be assigned as rutile phase of pure SnO2 except (111) is attributed to cubic phase. The optic analyses have shown an average transmittance between 70 and 90%, and showed a direct band gap reducing with increase in Fe doping (3.82–3.72 eV) and Ni content (3.82–3.69 eV). AFM images have revealed that surface roughness is affected strongly by deposition conditions and dopant contents.

The development of highly efficient and stable inexpensive catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 in an aqueous solution by utilizing metal-organic frameworks (MOFs) as precursor and template remains a hot topic. Herein, a simple self-template strategy was developed to synthesize a porous nitrogen-doped carbon frameworks embedded with zinc and cobalt nanoparticles (Zn0.3Co2.7@NC) catalyst by thermal annealing of the bimetallic zinc-cobalt zeolitic imidazolate framework (Zn0.3Co2.7-ZIF) as an effective precursor and template. The resulting Zn0.3Co2.7@NC catalysts show an excellent catalytic activity for the reduction of 4-NP and the reduction reaction was completed only in 5 min with nearly 100% conversion. The apparent rate constant for the reaction of 4-NP reduction was estimated to be 0.683 min−1. Moreover, the catalyst was extended to reduce other nitro compounds and exhibited excellent catalytic activity. When compared to other related catalysts in the literature, the catalytic activity of catalyst is superior. Therefore, the resulting Zn0.3Co2.7@NC is expected to get more extensive application in the field of catalysis.

In this work, the hybrid carbon nanofibers (Cu2O/CNFs) containing cuprous oxide (Cu2O) nanoparticles were prepared by a convenient electrospinning method and following a carbonization treatment. The morphology, composition, and microstructure of the Cu2O/CNFs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffractometer. The as-prepared Cu2O/CNFs exhibited a stronger absorption in the range of 250–700 nm. The band gap energy of the Cu2O/CNFs was estimated to be 2.0 eV. Due to the synergistic effect between photocatalytic activity of Cu2O and excellent adsorption capacity of CNFs, the obtained Cu2O/CNFs exhibited excellent photocatalytic activity for degradation of rhodamine B (RhB) and phenol. The possible mechanism for degradation of RhB and phenol degradation were also discussed. The resultant hybrid carbon composites offer the significant advantages, such as low dosage, high catalytic activity, easy recycling, and excellent stability. We hope that the resultant hybrid composite Cu2O/CNFs could be applied as catalytic materials for further application in the future.

A consistent description of the hydrogen permeation through metal membrane based on hydrogen chemical potential proposed has been explained in detail. The hydrogen flux is proportional to the PCT factor, f PCT, consistently, which reflects the shape of the pressure-composition-isotherm (PCT curve) of the material. In addition, in view of the PCT factor, f PCT, and the ductile-to-brittle transition hydrogen concentration, DBTC, a concept for alloy design with high hydrogen permeability and strong resistance to hydrogen embrittlement has been proposed. In this concept, it is important to design alloy composition with appropriate PCT curve under the given pressure and temperature condition. As an example, V–9 mol% Al alloy has been designed, which exhibits high hydrogen flux without brittle fracture under given condition. Thus, the new consistent description is useful not only for the understanding of the hydrogen permeation property but also for the alloy design.